The GP Alkaline is ok. Suitable for low drain devices (toys). At least it doesn't leak like Energizer e2 Advanced (X91-Alkaline). Duracell is still a better performing battery compare to GP. My experience is that Duracell CopperTop is longer lasting than GP. While Duracell Ultra is suitable for high-drain devices (DigiCam, Flashlight).
Maybe you could consider Panasonic Alkaline (Digital Power). I've got a better runtime from it compare to Duracell (priced almost the same). The new Panasonic Evolta seems to gives stable performance from low to high drain devices. YMMV. I'm using Evolta in my EZ AA.
Same negative experience on the normal NiMH (AA and AAA) GP2700, GP2500, GP2100, GP1000 (AAA). Not only it loses its capacity after a few charging cycles, some cannot be charge at all. The GP1000 (AAA) is the worst, 8 out of 12 pcs that I have cannot be charge after 5-7 cycles. While I still hold a few of the GP2700, gave the rest of the GP2500, GP2100 to garbage collector for recycle.
The newer GP ReCyko+ seems to be better (for now), been using the AA and AAA with their Quick Charger (6 hours+). So far only 1 out of 10 pcs of the ReCyko+ AAA fail to charge after 5 cycles which just happen today. No problem so far for the ReCyko+ AA, 8 out of 8 still charging after 5 cycles.
Besides GP ReCyko+, I'm also using Sony CyberEnergy Blue (LSD, Japan and China made) and Sanyo Eneloop. All three LSD battery brands giving comparable results, but I'm leaning towards Sony (Japan made) and Sanyo.