Nah, no way is it an improved season from season 4, imo it was a downgrade of the SpongeBob series after season 4. Season 4 had some great episodes I like which are Patrick SmartPants, Selling Out, and I also even like Shell of a Man, Krabs VS. Plankton, and The Lost Mattress. Sure The Lost Mattress may of had some Squidward abuse in it, but I didn't think it was that bad and enough to ruin the episode.
Back to season 5, there was just way too many gorss episodes that were the most disgusting in all of history, and not only that, but a lot of episodes had some poor and feeble plots like The Krusty Plate and Blackened Sponge. I'm glad this season is over with now.
Because I sure do love season six and seven episodes of SpongeBob, there's hardly any at all that I dislike in seasons 6 and 7 actually come to think of it... The only really bad ones I can think of are Penny Foolish and The Splinter. Season seven rocks with episodes like Toy Store of Doom, Ditchin', and Porous Pockets.