Some years ago, I germinated some Meyer Lemon seeds and have used them as rootstocks and gave away to friends as gifts.

Here's my notes of the cultivars that I have tried using multigrafts on the same Meyer rootstocks. The following cultivars grafted to them were vigorous, productive and have higher quality fruits compared to if you buy these same cultivars already grafted to whatever the nursery uses:
Tarroco
Sudachi
Vainiglia Sanguigno
Ponderosa Lemon
China Satsuma S-11
China Satsuma S-9
Most of UCR's mandarins
Yuzu

And the cultivars that were poor growers, or showed some incompatibilities, or not so good fruits:
Navels (Navelina, Spring, Lane Late, Navelate, Marss Early, Fukumoto)
Valencias (MidKnight, Delta, Late, Rohde Red)
Limes (Ginger, Key, Bearss, Black Twig)

Most are not replicated but if you have your own experiences, kindly post them here and we can compare.

Joe, since Meyer seedlings are not true, won't each of the seedlings be different?

Yes that's true. There is also quite a big chance that the seedling will have majority of phenotypic characteristics similar to the original Meyer lemon, although genetically they would not be identical. So for commercial application, Meyer lemon is unreliable as rootstock. But for a home grower, this is just a sample of what you can try out. Comparing notes with others we may hope to get a pattern of either reliability or unreliability as rootstocks even if genetically, the rootstock seedlings are not technically clones. Was just trying to see if others have tried them, and for now am not suggesting nor recommending them as rootstocks but I could not prevent anyone from doing so. For one thing, these are not cold hardy as other common rootstocks but for me they are worth the small experimentations with nice rewards of fruits for personal purposes as a hobbyist.

Most promising updates so far is that when the Meyer Lemons served as my interstock, they seem to improve the quality of the cultivar fruits that are graft compatible with it.

For example, I noticed that some of my mandarins were lousy tasting on Lisbon lemons, but those grafted unto Meyer Lemons which in turn was grafted unto Lisbon, the quality seemed to be better. I need more confirmation this coming harvest season in winter.

I also noticed that if you buy the cheap grafted Meyer Lemons in citripots (4"x4"x18") and use them as "rootstocks", technically, they are interstems, I also noticed that fruit quality are excellent. Unfortunately, there are no labels of the original rootstocks on them.

My sister Beth has a meyer seedling that was given to her by a friend-- it came up as a volunteer under a Meyer Tree. It is pretty thorny. I bark grafted with a mandarin. The graft took and is growing, so we can compare results later. This would also be a test of cold hardiness, since Beth is in an area that gets a little more cold than I do.

I have a Meyer Lemons that has several branches. I would like to make a cocktail tree of different lemon varieties. It sound like grafting onto a Meyer may be a good idea, at least for good fruit. These are the ones I think I well try.

Ponderosa Lemon
Seedless Lisbon
Variegated Pink Eureka

Now I have never grafted before but I hope to be successful.

So far this year I have grafted 10 different varieties into a Meyer lemon. Six of them were done a few weeks ago and the Clementine is showing new growth. The others are still green so just waiting for them to grow.

Clementine
Naval Orange N-33
Lemonquat
Ponderosa Lemon
Key Lime
Thornless Mexican Lime
Rio Red Grapefruit
Dancy Mandarin
Variegated Satsuma
Seedless Lisbon Lemon

The last four are the ones I added this week

any updates on this , i just finished grafting a whole bunch of varieties on my meyer lemon seedlings.
any uncompatabilities or big flavor differences