Seidio 3500 impressions along with 2600.
1. You usually get what you pay for (this battery rocks) and the 2600 did not.
2. The 2600 I had was junk. Cell charge retention depleted to about half it's life within a week (about equal to 1300 stock).
3. The 3500 is a beast in a good way.
4. I still think $63 is too much for a battery, but I go back to item 1.
5. The cover/door is sturdy and built well (for plastic).
I will not bother trying to equate use, since too subjective, but I use the heck out of my Inc for surfing, games, videos and MP3, and this puppy lasts the day and still has 60%. The 1750 had a little juice left at the end of the day, so the 3500 seems to correlate to 2X or better than the 1750. It seems like more than 2X, but again, usage is too subjective to peg it.
If you use the heck out of your Inc, the Seidio 3500 is a good buy. Then again, if you do not mind carrying extra batteries and restarting, there are cheaper options. I do not like carrying extra batteries and restarting. I will keep the 1750 as a backup when I travel, though.