It was the OTL Finnish campaign that first of all had Hitler believe that attacking SU was a matter of kicking in the door, and the whole house comes down.
As going east was the whole "raison d'etre" behind nazism, Hitler will attack anyway, but if allowing for a campaign to be planned into 1942 I'll second Grimm Reaper in a prediction of big trouble for the Soviets.
I also doubt that the absense of an independent Finland in 1941 will help the Soviets. If they need an effort like that Blue Max describes to keep Finland subdued, it will truely be a resource drain. Next the northen front was the part clearly given the least priority by both Germany and SU in OTL 1941. Armygroup North was much weaker than the two others and Leningrad practically was undefended in OTL late summer of 1941. It wasn't the presence of Finland and their participation that made the difference in taking Leningrad or not, but rather von Leeb (commander of Armygrp. N.) not taking the chance when he (perhaps) for a short moment had a window of opportunity.
With no independent Finland it will be even more obvious to von Leeb that he need to take a risk to take Leningrad, and that he need to act fast. That is if the Germans give priority to this front at all. It will not need much less attention than that of OTL, before it only is a demonstration. If more forces, German as well as Soviet are taken from the northern front to the central or southern, it will mean more fighting in terrain more suitable to German blitzkrieg tactics. Combined with the effects of the Germans actually being prepared for a lengthy campaign - it smells of really bad hair day for the Red Army.
It is of course also of importance how/why the Finnish campaign goes better in this ATL. In OTL the Red Army took some important lessons from its defeats, not at least in fire co-ordination, which was important when the Red Army ould go on the offenisive later. But if the PoD is mainly luck, like in having the Finnish collapse quickly (some political PoD on Finnish side), the Red Army will be a step behind when it comes to rebuilding the Red Army. The officers that defeated the Germans were in the academies in 1941 being taught tactics adjusted from the Finnish campaign.
If the PoD is the Red Army being a lean mean war machine not short of maintained equipment or well educated staff officers - well then it of course is a very different matter...
Regards
Steffen Redbeard