All that there is to say is that lack of games is the biggest issue.
Allow me to explain: Having owned my system since a month after release I have managed to juice more than 200 hours out of this apparently lacking system. I won't lie here, a good chunk of that is from my original DS games but that makes up no more than half of this. If that value is anything to go by, the 3DS' feel isn't as cramp inducing as I hear people say. Nor is it heavy, a complaint made by gamespot staff. Complaints I can agree with are that the thin-ness of the L and R buttons is weird, and using the D-Pad is horrible for SSFIV. The position and size of the D-Pad are what eat at me, but some (out of preference) complain about the clicky/button-like movement it has.
So allow me to address another issue: Battery Life. Nintendo said '5 hours' and apparently everyone else agrees. Well, no. Admittedly most of my time is spent with the 3d off (like how I never had sound on my DSLite to save battery life), sound half way, brightness on 2/5 and power saving mode on, it lasts me 12-15 hours, but these choices don't hinder my gameplay experience very much. Which brings me to the 3d effect of which many things are said. Things like headaches and such, I don't know if this is a case of people only noticing them because they've been warned about them or if there's different levels of resistance (for lack of a better term), but I have yet to experience any at all, even in the first few weeks where my 3d was always on. People also say it's very subtle, again this may be people see it in different ways but for me and everyone I've showed it to, it's been amazing.
And then there's the graphics, this appears to suffer from a misconception among many that think the 3ds is just a slight upgrade from the DS. Think of it this way, SSFIV runs fine with graphics comparable to that of its console counterparts and looks even more impressive in 3d. This suggests to me that the graphical capabilities are close to those of the GameCube but looks better because of the lower resolution covering up poorly detailed sections. That's not to mention the potential that may be held in the memory capacity of the cartridges themselves (see any RareWare game) and what could be exploited in the games themselves.
To close, I disagree with most complaints about the 3ds for reasons stated above. The biggest complaint I have about the system is a lack of games that I didn't complete years ago and everyone I've shown the system to has made that point themselves. Essentially, there is no issue in buying the 3ds now, what with some big titles such as Mario 3d Land and Mario Kart 7 on the way, but there's no harm in waiting for the release of more games such as Kid Icarus, a bonus being you can pick up the Mario games cheaper at that time too.