My problem with the Paul Ryan budget is effectively my problem with any other budget. While bipartisan in its conception, it would be highly partisan in its execution. If the Republicans did hypothetically "sweep" Washington D.C. and obtain both houses of congress, the White House, and in a few years time the Supreme Court of course roadblocks would be lifted- any party could get something done under these conditions so long as the opposition isn't majorly galvanised against them to form a fierce minority of just enough size to block any initiatives ('08-'10 senate). Seeing how the Democrats lack a major left wing push at the moment, this would be somewhat unlikely in a hypothetical Republican sweep.
Now then, with the Republicans calling all of the shots and knowing it... you can guess where this would go. While Romney could propose all the budget cuts he wants, ultimately the military will see increased spending with tax cuts on the wealthy while welfare programs are left to decline. The fact is, a bipartisan budget would have a snowflake's chance in hell under a Republican sweep, and we would just go back to a good old Republican budget where we still spend more money than we make and program's that the average person can use are scrapped for tax cuts at the top and a trillion dollar+ military. The bipartisan system, for all it's flaws, tends to keep representatives of 55% of the population from having all of the power. I'd rather not see what would happen if a single party earned all control in a time as partisan as this.
Obama is the only way to keep the necessary inefficiency that forces Washington to have some accountability.
Also, the idea that Democrats are "blocking" Republicans in some way is ridiculous. It's a Democratic presidency that also holds one house. I'll go right back at it and say that Republicans are blocking Democrats. It's the inevitable gridlock that comes up from time to time in a two party system and no party is more responsible than the other as both have no desire to negotiate.