Ratchet's weapons level up with use and can become really powerful, really quickly. Guns earn experience every time you hit an enemy and, as they level up, become more powerful. Areas tend to be stuffed with enemies, so even after purchasing a weapon late in the game, it doesn't take long to max it out.
Ratchet & Clank Future: A Crack in Time also introduces a new upgrade system for weapons that lets you further customize weapons. Add-ons are scattered throughout the galaxy and offer things like rapid fire, exploding shells and other slight tweaks. None of the upgrades is necessarily more powerful than the other, causing the system to feel like a real customization kit and not just another way to level up weapons.
The biggest addition to Ratchet's side of the game brings back two of my favorite features. While zooming between planets, you can engage in a little space combat with enemy ships and even take missions from wayward travelers. Flying is restricted and few of the ship's capabilities, like barrel rolls, go under-utilized, but overall the areas are still fun. Additionally, you can land on moons and run through spherical planet levels in pursuit of weapon upgrades and Zoni. These areas provide a few platforming challenges, some of which aren't intentional. The camera can become uncooperative when traveling around planets, especially when jumping.
Ratchet & Clank Future: A Crack in Time is the sum total of all the tweaks, changes and features found in past games. It may be "more of the same," but that isn't a problem.