Why not take you 7D into the local shop and ask to try some, take the
results home and have a look for yourself.

If you want to keep the cost down a bit apparently the Sigma 18-200mm is
reasonable and worth a look.

K/Minolta is coming out with three new lenses made specifically for
their digital cameras (Dynax/Maxxum 7D,5D) . I haven't been able to
find any for sale yet and K/M has not answered my request for sales
info. Anyhow the lenses are:
AF DT 11-18mm f/4.5-5.6 (D)
AF DT 18-70mm f/3.5-5.6 (D)
AF DT 18-200mm f/3.5-6.3 (D)
You may want to wait and check these lenses out.
  <<<Adam R>>>
********************************************************

I am curious about your comment that the 28-200 will not focus to infinity.
Is this with manual or autofocus?
Have you made exposures comparing manual and autofocus and at different f
stops?
You may feel that the 24mm lens is the sharpest because it has the greatest
depth of field because of its shorter focal length.
What I am getting at is that if all your lenses are underperforming then
something may be wrong with the way you are using the 7d or with the camera
itself. You may not have the world's sharptest lenses (who does?) but the
lenses you have listed should all be reasonably adequate performers, in
terms of apparent sharpness, with the 7d, possibly better than with film
because the digital sensor only sees the central part of the image circle
made by the lens.
You really should evaluate theses issues before spending money on new
lenses.

Congratulations.  A great camera.

Just crack open your wallet as follows:

    Maxxum 28-70  f/2.8 G (or the new 28-80 f/2.8 G D) -and-
    Maxxum 80-200 f/2.8 G (or the new 70-200 f/2.8 G D, etc.)
    Maxxum 100 f/2.8 macro -or-
    Tamron 90mm f/2.8 macro

If you're goung to be doing a lot of portraits, then consider the 50mm
f/1.4 or 85mm f/1.4.  (Even the modestly priced 50 f/1.7 should do well
for most portraits.)  You can do portraits with the 28-70/80 with great
care to keep the camera level/square wrt the subject, but your error
rate (poor perspective related distortion) will be higher.

    Personally, I'm thinking of adding the Maxxum 17-35 (either the f/3.5
"G" version, or the Tamron (badged Minolta) f/2.8 - f/4 (D) version).
Or a Nikon Coolscan 9000 and used RZ67. Or... <sigh>  Whatever, I need
an MF camera by September and the scanner to read it.

My SO has the 28-200 (Sigma) and she works hard with it to get very good
results (Maxxum 5).  But I also know when she uses the 50 f/1.7 that she
gets great reults that exceed the Sigma in contrast and color.

Cheers,
Alan.