Just at the store this past weekend and I was shocked that they already have tomato's and peppers and herbs. I couldent help but notice the tom's were on average 6" tall and my seedlings at home are a mere 2" or so! I just transplanted them to larger pots so I'm hopefull that they will now shoot up. I usually plant around memorial day. Do these sizes seem ok?
Don't worry about it, the seedlings would get big enough before then. Once the seedlings get past the initial shock of up potting, it will grow like gangbusters, doubling every week or so. your 2" seedling could easily reach 8" in 2-3 weeks.
I have the same planting date you do and my tomatoes are just sprouting. They can go in the ground at 6" tall, but there is plenty of time as long as the plants have good nutrition for them to get up to 8-10 inches tall. The last couple of weeks it is usualy warm and sunny outside during the day and the plants can put on alot of growth as long as you bring them in on the cold nights.
The stores are jumping the gun this year for some reason. There are going to be a lot of frost killed plants around the country by people trusting the stores.
The gardening bible book I have says that's the exact problem with store-bought seedlings...they're not at the right stage of growth most of the time for your zone. Often they are too far along when you buy them, which is usually before the last hard frost, so you have overly mature plants with under-mature root mass going into the ground.
the seedlings you started are likely right on par for your zone.