Logitech has stealthily released the Harmony 510, a new entry-level $100 universal remote that slightly reworks the design seen on the company's previous 500-series models. It's almost an exact copy of the Harmony 550, except for a different color scheme and slight reworking of the keypad. There are two fewer keys, and some buttons are relabeled. For instance, the bottom four buttons on the 550 are Sound, Picture, A, and B; on the 510, there are just four unlabeled colors (red, green, yellow, and blue). In fact, those color keys are actually borrowed from the European versions of the Harmony remotes--note the very similar Harmony 525.
To confuse matters further, there's a third remote--not counting the now (presumably) discontinued Harmony 520 and the Europe-only 525--in the line that's also a near-doppelganger: the awkwardly named Logitech Harmony Advanced Universal Remote for Xbox 360 (which we dubbed "AURX360", strictly for expediency's sake). Even for non-Xbox 360 owners, that model may actually be the pick of the litter, because it has a couple of extra buttons over the 550--and controls 12 devices, rather than just the 5 the 510 does. All four U.S. models can be found online for under $85 dollars.
We haven't reviewed the 510 yet, but it's a safe bet that the reviews of the other three models linked above will give you a good idea of what to expect on the new model. If you're looking to spend more than $100, check out the our list of best universal remotes, which includes higher-end models, such as the Editors' Choice Logitech Harmony One.