For some reason the fact that motion controls (or "gestures") are a major part of the Wii control interface bothers people; it is felt that this ruins the gaming experience and that the majority of such implementations would be better served by traditional digital button presses. Indeed some people go so far as to desire all Wii games to have support for the Classic or Gamecube controllers and not even use the packed-in Wii Remote + Nunchuk controls at all, much less the gestural component. You don't have to read too many online game previews or reviews without seeing some mention of "waggle controls" - even if the game lacks any gestural input at all!
When looking at the history of console gaming we see that for the most part controls have consisted of digital input, with the odd trackball or rotary analogue device. Many people moaning about Nintendo's choice of using gestures forget that the move to analogue thumbsticks as the default directional input device on the consoles of the mid-90s to today was similarly decried and rightly so: in the majority of cases the only purpose of analogue control is to provide some kind of unnecessary incremental movement animation for a character in a 3D action game.
The only places it really benefits the player is in flight sims and driving games; there aren't many of the former and a thumstick is a pretty poor interface for the latter. Really you may as well still be using a d-pad and in games with a more arcade styling you'll have better results. Nevertheless Nintendo and Microsoft have both decided upon controllers with the d-pad relegated to a secondary position and without continued cries about "tacked on" analogue control.
The simple fact is that gestures are more readily grasped by people who wouldn't normally play video games, and even sceptics should agree that playing Wii Sports Tennis is more fun waving a wiimote than fiddling with a joypad. The reasons for disliking gestures due to a tacked-on nature should be focusing on developer game design, rather than the interface itself. A wiimote motion isn't more or less legitimate than a button press from a mechanical perspective - it's just a different way to send a signal - but sometimes the use of these gestures rightly deserves some criticism.
Some developers try to do too much with gestures and don't appear to recognise the limitations of the motion detection hardware in the Wii Remote and Nunchuk. The wiimote is clearly sensitive to motion as Let's Tap! attests, using vibration of the wiimote through the box it's resting upon to play the game.
The Nunchuk's detection of rotation is also good enough to be used to rotate the camera in Marvel Ultimate Alliance . However it's clear from gesture implementation in games like Godzilla Unleashed, Rampage Total Destruction and Marvel Ultimate Alliance that distinguishing between movements in opposite directions isn't quite as easily done and a motion in the opposite direction of the motion intended is frequently registered. Given the difficulty of detecting an upward or downward wiimote motion generally in these three games it's clear that further adjustment of the motion controls was required; the developers may not have taken the time or have been given the opportunity to properly implement the controls.
Failure to distinguish between motions in opposite directions is likely due to the motion being too quick for the Wii to pick up until the move back to a neutral position happens. Alternatively the motion detection sensitivity has been set so high that rapid movements are being ignored (because they overload the sensor) and more subtle return motions are picked up. Whatever the reason, it appears developers have to put more effort into tuning the controls and working around the interface limitations.
De Blob uses a downward motion to perform jumps and slam targeted enemies with great results. This appears fairly simple, but the game also successfully discerns left/right motion when jumping off the side of a building which involves motioning away from the surface your character is attached to. Deadly Creatures uses controls that accept input which is either up/down or left/right eliminating the issues associated with false detection of motion in the opposite direction and also allows users to tune the gesture sensitivity - something more developers should consider. This same game also features Quicktime sequences which call for - and detect - movement of the wiimote and nunchuk away from each other.
As well as addressing motion detection issues we should look upon use of motions for repetitive actions as a poor game design decision; not as an indictment of motion control in general. Marvel Ultimate Alliance uses a quick left-right motion as a primary melee attack; given the ongoing battles with henchmen and goons throughout the game this is clearly a poor decision and leads to rapid tiring of the forearms. Thankfully this same action can be carried out with the A button instead.
Mushroom Men also uses a wiimote wave to carry out melee attacks, but has no button alternative which suggests a lack of consideration for how long people will play the game in one sitting. Deadly Creatures was to have a similar use of motion for primary attack, but the developers made a decision to delay release of the game to swap the gesture for a button press, citing player fatigue as the reason and rightly so.
Time will tell if Microsoft and Sony embrace motion control in their future consoles and give it a position as prominent as that of the analogue thumbstick. Clearly Nintendo has made a great success of drawing in new customers who would otherwise not participate in gaming. The notion that standing and waving a remote in the air looks "daft" or "uncool" compared to sitting with a small wedge of plastic and rapidly fiddling with it appears to be a minority view given how many people have been ready and willing to mime Tennis and Bowling on their Wiis. I'm sure they would rightly regard controller fiddling as the less appealing activity.