I thought he pulled up trees at Rangers from what I observed. Looked like Celtic were never going to be challenged after winning what seems like 60 titles in a row! Ranger's ascension may be in part down to Celtic's own problems however, last 3-4 years they haven't seemed quite as invulnerable.....
They say winning the league is the 'easy' part, defending titles is where it's at. Who can forget Chelsea's mid-table capitulation after lifting the title, even Man City struggle to emulate their own standards.
Scottish teams get a rough deal when it comes to Champions League qualification too, so I'd imagine if that fails (and most teams in it will have some pedigree) then the slog of a two-horse domestic title race becomes rather wearisome after a while.
Ultimately, the Scottish league is a farmer's league where managers go to build their standing in the game, or to repair it, a la Brendan Rogers, Martin O'Neill etc. Gerrard's Villa won't set the Premier League alight but they'll be better off for having had him cut his teeth in Scotland. Much like I expect Lampard at Norwich to help him develop as a manager as opposed to being thrust into a top job too early.