They're actually reasonably good value, all told, in my opinion.
I bit the bullet and am now a 3star V.I.P until June. Immediate boost in credits (I think it's 42 straight off for a level 3 VIP), 4 credits a day, which soon mount up for the additional one off sponsorships and are useful for advertising your match, which I found was a very quck way to sell out the stadium.
Plus you can cash a voucher in every two seasons for 180 credits, which can then be converted to cash through those sponsorships.
They speed things up initially, helping gain the finances to upgrade facilities/improve the team more quickly, but like the game blurb says, they are less important as you progress and you really can play the game without them.
If that remains the case, we'll see.