I have an Undercover hard tonneau and IMO they are the best thing since sliced bread. They are very light( mine weighs just 58lbs for an 05 Extended Cab standard bed ), extremely strong( you can stand on them ), are very affordable( I paid $570 ), lock for security, and are extremely easy on and off( two split rings at the front come off then just unsnap the struts and it lifts right off - 45 seconds with 2 people - 2 minutes alone ). They even come with a nice little LED utility light now. Amazing how bright those 3 little LED's are when it is dark out.
Only a couple drawbacks of sorts. The 1st is you obviously can't just pop it off at Home Depot if you buy something really big. You do need to remove it at home 1st( you can not drive with these covers up - they must be down and locked due to the easy off method they use - just not safe ). The other is they are not ideal for painting if you want a color matched HT for your truck. They can be painted but there is a lot of prep involved plus the surface is textured. That means metallic paint will look splotchy. The flake will pool in the little pockets of the texture. Solid colors are okay. Pretty $$$ to prep and paint an Undercover though. They come as a semi gloss black and the finish really is tough and lasts. Looks great on most colors as is.
I will never use another tonneau on my trucks. Of course I need the security of the locking feature so the soft covers are out. Of all the hard covers out there, short of the extremely expesnive roll to open ones, the Undercover is the most user friendly.