[quote name='rapsodist']Tools of Destruction was perhaps the weakest Insomniac contribution to the series to me (its status as the first HD upgrade notwithstanding). But that's not any real knock on its quality; I'm just talking about the difference between great and good. It's still one of the finest games you can find on PS3. It was simply the first game that made me tire slightly of the series' conventions, similar to how I tired of Twilight Princess' perpetuation of Zelda's conventions. (A Crack in Time has thankfully remedied some of my concerns, though at the cost of more exploratory levels.) If you're any fan at all of the Ratchet series, it goes without saying that you should pick this one up.[/QUOTE]
I think it's less that the conventions were tiring as that they weren't even used as well as in previous games. In previous games there were a lot of places that you'd travel through and not be able to reach and then later, on another planet, you'd have this neat moment where you get a new weapon or gadget and go, "Ah ha! Now I can go back there and get to that area."
Tools of Destruction is a lot more linear, and thus less interesting since that sort of exploration has always been one of the highlights of the series.
Also, replacing the earlier space combat sections (and arenas, omfg I missed those in ToD!!!) with much weaker on-rails segments didn't help.
Still a very, very good game though. But it didn't make me want to jump right in and go through it a second time back-to-back like Going Commando did before it.