I don't proofread.
It's been slower for me, because of the fact that I have both Adobe Photoshop and Paint.NET installed, I mainly use Paint.NET as an alternative to mspaint because of it's speed in comparison to Adobe Photoshop. After updating to 4.0, it is indeed slow for me, before than, I could've had Counter-Strike Global Offensive running in the background and edit images between rounds on the fly without slowdown (for reasons). I can't really do that with 4.0, and in my opinion it felt slower than Photoshop too (just a little). At times, it lags when moving around pictures, the selection tool is laggy. The Line tool also suffers too.
And so, at the end, I've decided to downgrade back to 3.5, it's just my computer I guess, and it's really unfortunate that it slows down for me. Here are my specs.
Windows 7 Ultimate 64-bit
GA-MA700-DS3P
AMD Phenom 8750 Triple-Core Processor (3 CPUs), ~2.4GHz
4096MB RAM
DirectX 11
ATI Radeon HD 4800 Series (2303 MB) (Core 575 MHz) (Mem Clock 1004 MHz)
Also, Paint.NET 4.0 has the same feel as Photoshop too me, as if it's not "optimized for Windows" (my layman opinion).
I'm probably not gonna respond, I just logged in to file in my problem with 4.0